This brief tutorial on ROM closures (also known as parameterizations [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]} and hidden dynamics [8]}, [9]})
is structured as a sequence of simple questions and answers that lead the reader from a simple PDE to projection ROMs, and then to ROM closures.
Our paper is aimed at first year graduate students and advanced undergraduate students.
Thus, we strive to keep the technical details to a level that is easily understood by students with a standard background in differential equations and numerical methods.
We also emphasize that our goal in this tutorial is not to explain the “how,” but the “why.”
That is, we carefully explain the principles used to develop ROM closures, without focusing on particular approaches (which are carefully discussed in [10]}).
